We propose to study the effects of age on regulation of arachidonic acid (20:4) metabolism in vascular (arterial) tissue. Our hypothesis is: prostacyclin (PGI2) formation decreases with age. Increased blood pressure, decreased bleeding time, increased lipid peroxidation and an increased tendency to develop cardiovascular disease is associated with aging and is consistent with decreased synthesis of a potent vasodilator-antithrombotic hormone, PGI2. Although little is known concerning lipoxygenase activity in vascular tissue, it is plausible that increased activity of this enzyme with age and thus increased formation of its products, hydroperoxy fatty acids (HPFA), may inhibit PGI2 synthetase. We plan to qualitatively and quantitatively investigate 20:"4 metabolism in aortic tissue using high performance liquid chromatography (HPLC) and gas chromatography-mass specrometry (GC/MS). We will continue to study the difference in capacity to form PGI2 between young and old animals, measure the activity of lipoxygenase and PGI2 synthetase (as a function of age) in urine and plasma. We have found that high 02 on vascular 20:4 metabolism. An accelerated lipid peroxidation with age may imply that aortic tissue from older animals is more sensitive to O2 inhibition of PGI2 synthetase. Thus, we will study the effects of O2 on formation on PGI2 and HPFA in tissues from young and old animals. We also plan to study 20:4 metabolism in cultured endothelial cells, to determine the mechanism of hormone-stimulated 20:4 release and to examine the possibility of differential sensitivity with age to hormone stimulation of 20:4 release and metabolism. In addition we plan to carefully study the effects of nicotine on PGI2 synthetase in cultured cells. Prostaglandin and HPFA products of 20:4 metabolism will be determined using HPLC and GC/MS techniques developed by us. In the experiments proposed to study PGI2 levels in vivo we plan to develop a relationship between PGI2 production and age from birth through adulthood. Animals will be sex-matched. Points along the curve showing greatest differences in PGI2 production will be used as reference for other studies planned.